Network system, control method, and gateway

Abstract

To prevent a packet loss during hand over, provided is a network system including: a gateway coupled with a wired network; and at least two base stations coupled with the gateway over the wired network and providing a wireless access method, in which the gateway is configured to: calculate, for each of the at least two base stations, a delay in information transmission between the gateway and each of the at least two base stations; choose a maximum delay from among the calculated delays of each of the at least two base stations; calculate, as a delay difference of each of the at least two base stations, a difference between the chosen maximum delay and the delay of each of the at least two base stations; and notify each of the at least two base stations of the calculated delay difference of each of the at least two base stations.

1 . A network system, comprising:
 a gateway coupled with a wired network; and   at least two base stations coupled with the gateway over the wired network to communicate information between the gateway and each of the at least two base stations, the at least two base stations providing a wireless access method, wherein the gateway is configured to:   calculate, for each of the at least two base stations, a delay in information transmission between the gateway and each of the at least two base stations;   choose a maximum delay from among the calculated delays of each of the at least two base stations;   calculate, for each of the at least two base stations, a difference between the chosen maximum delay and the delay of each of the at least two base stations; and   notify each of the at least two base stations of the calculated delay difference of each of the at least two base stations.   
   
   
       2 . The network system according to  claim 1 , further comprising a subscriber station which can be coupled through the wireless access method, wherein each of the at least two base stations is configured to:
 communicate with the gateway through multicast route; and   transmit the information communicated through the multicast route and received from the gateway to the subscriber station with a delay determined based on the notified delay difference.   
   
   
       3 . The network system according to  claim 1 , wherein:
 the gateway transmits to each of the at least two base stations a first control packet including a time of transmission at which the first control packet is transmitted from the gateway;   each of the at least two base stations transmits, upon reception of the first control packet, a second control packet to the gateway, the second control packet including the time of transmission which is included in the first control packet and a time of reception at which the first control packet is received by each of the at least two base stations; and   the gateway calculates, upon reception of the second control packet, a difference between the time of reception and the time of transmission which are included in the second control packet, to thereby calculate a delay in information transmission between the gateway and each of the at least two base stations.   
   
   
       4 . The network system according to  claim 3 , wherein the gateway transmits the first control packet to each of the at least two base stations through multicast route. 
   
   
       5 . The network system according to  claim 3 , wherein the gateway transmits the first control packet to each of the at least two base stations through unicast route. 
   
   
       6 . The network system according to  claim 1 , wherein:
 each of the at least two base stations transmits to the gateway a control packet including a time of transmission at which the control packet is transmitted from each of the at least two base stations; and   the gateway calculates, upon reception of the control packet, a difference between the time of transmission which is included in the control packet and a time of reception of the control packet, to thereby calculate a delay in information transmission between the gateway and each of the at least two base stations.   
   
   
       7 . A control method of controlling information transmission timing among at least two base stations in a network system including a gateway coupled with a wired network and the at least two base stations coupled with the gateway over the wired network to communicate information between the gateway and each of the at least two base stations, the at least two base stations providing a wireless access method, the control method comprising:
 calculating, by the gateway, for each of the at least two base stations, a delay in information transmission between the gateway and each of the at least two base stations;   choosing, by the gateway, a maximum delay from among the calculated delays of each of the at least two base stations;   calculating, by the gateway, for each of the at least two base stations, a difference between the chosen maximum delay and the delay of each of the at least two base stations; and   notifying, by the gateway, each of the at least two base stations of the calculated delay difference of each of the at least two base stations.   
   
   
       8 . The control method according to  claim 7 , wherein:
 the network system further comprises a subscriber station which can be coupled through the wireless access method; and   the control method further comprises:   communicating, between each of the at least two base stations and the gateway through multicast route; and   transmitting, by each of the at least two base stations, the information communicated through the multicast route and received from the gateway to the subscriber station with a delay determined based on the notified delay difference.   
   
   
       9 . The control method according to  claim 7 , further comprising:
 transmitting, by the gateway, to each of the at least two base stations a first control packet including a time of transmission at which the first control packet is transmitted from the gateway;   transmitting, by each of the at least two base stations, upon reception of the first control packet, a second control packet to the gateway, the second control packet including the time of transmission which is included in the first control packet and a time of reception at which the first control packet is received by each of the at least two base stations; and   calculating, by the gateway, upon reception of the second control packet, a difference between the time of reception and the time of transmission which are included in the second control packet, to thereby calculate a delay in information transmission between the gateway and each of the at least two base stations.   
   
   
       10 . The control method according to  claim 9 , further comprising transmitting, by the gateway, the first control packet, transferred through multicast route, to each of the at least two base stations. 
   
   
       11 . The control method according to  claim 9 , further comprising transmitting, by the gateway, the first control packet, transferred through unicast route, to each of the at least two base stations. 
   
   
       12 . The control method according to  claim 7 , further comprising:
 transmitting, by each of the at least two base stations, to the gateway a control packet including a time of transmission at which the control packet is transmitted from each of the at least two base stations; and   calculating, by the gateway, upon reception of the control packet, a difference between the time of transmission which is included in the control packet and a time of reception of the control packet, to thereby calculate a delay in information transmission between the gateway and each of the at least two base stations.   
   
   
       13 . A gateway that is coupled over a wired network with at least two base stations for providing a wireless access method and communicates with the at least two base stations, comprising:
 a processor which performs computing;   a memory coupled with the processor; and   a network interface coupled with the wired network, wherein the processor is configured to:
 calculate, for each of the at least two base stations, a delay in information transmission between the gateway and each of the at least two base stations; 
 choose a maximum delay from among the calculated delays of each of the at least two base stations; 
 calculate, for each of the at least two base stations, a difference between the chosen maximum delay and the delay of each of the at least two base stations; and 
   notify each of the at least two base stations of the calculated delay difference of each of the at least two base stations.   
   
   
       14 . The gateway according to  claim 13 , wherein the processor is configured to:
 transmit to each of the at least two base stations a first control packet including a time of transmission at which the first control packet is transmitted from the gateway;   receive from each of the at least two base stations a second control packet including a time of reception at which the first control packet is received by each of the at least two base stations; and   calculate a difference between the time of reception which is included in the second control packet and the time of transmission, thereby calculating a delay in information transmission between the gateway and each of the at least two base stations.   
   
   
       15 . The gateway according to  claim 14 , wherein the processor sends the first control packet, transferred through multicast route, to each of the at least two base stations. 
   
   
       16 . The gateway according to  claim 14 , wherein the processor sends the first control packet, transferred through unicast route, to each of the at least two base stations. 
   
   
       17 . The gateway according to  claim 13 , wherein the processor is configured to:
 receive from each of the at least two base stations a control packet including a time of transmission at which the control packet is sent from each of the at least two base stations; and   calculate a difference between the time of transmission which is included in the control packet and a time of reception of the control packet, thereby calculating a delay in information transmission between the gateway and each of the at least two base stations.